Digital printing methods such as inkjet printing are becoming increasingly important for the printing of textiles and offer a number of potential benefits over conventional printing methods such as screen printing. Digital printing eliminates the set up expense associated with screen preparation and can potentially enable cost effective short run production. Inkjet printing furthermore allows visual effects such as tonal gradients and infinite pattern repeat sizes which can not be practically achieved with a screen printing process.
However, inkjet printing as it exists today suffers from relatively slow speed. To be competitive with screen printing even for short runs, the speed of inkjet printers needs to increase. One means for increasing speed is to develop larger “industrial” printheads having a greater number of nozzles that are compatible with aqueous ink. Such heads have recently become available from companies such as Spectra Inc. (Hanover, N.H. USA) and Hitachi Koki Imaging Solutions (Simi Valley, Calif. USA). Previously, heads of this sort were only available for solvent inks and were not suitable for jetting aqueous inks.
Printers adapted to use these aqueous compatible industrial printheads are being developed. Suitable commercially available inkjet printers designed for textile printing include, for example, DuPont® Artistri® 2020 and 3210 Textile Printers (E.I. du Pont de Nemours and Company, Wilmington, Del.), Textile Jet (Mimaki USA, Duluth, Ga.), DisplayMaker Fabrijet (MacDermid Color Span, Eden Prairie, Minn.), Amber, Zircon, and Amethyst (Stork®).
Among the colorants utilized in textile printing are disperse dyes, which have proven to be especially useful for printing on hydrophobic fibers such as polyesters, cellulose acetate, etc. The initial choice of dyes for digital printing are often suggested by those used in screen printing. However, the need for specific disperse dye systems for digital printing of textiles require multiple levels of optimizing ink properties such as jettability, stability, shelf storage, color properties, etc. The color intensity of a digitally-printed textile needs to be improved for full adoption of this printing option for textiles.
For most, if not all, of the digital ink/textile combinations, there is a significant need for a blacker black. Not only is there a need for a higher optical density black when printed at 100% coverage, but also for areas of a print the require less than 100% black coverage, such that the black remains black and does not appear to have a different color hue other than a black. For black inks made up of disperse dye colorants, low coverage black printed areas can often have undesirable shading to another color.